Question

Write the equations for the identification of ammonium ions. State observations​

Answer 1

Identification of cations (positive ions)
Identifying metal cations by using flame tests
The principle here is that the salts of some metals will impart a colour to a non-luminous Bunsen flame.
Test
1. The technique is first of all to clean the end of a piece of platinum or nichrome wire by dipping it into clean hydrochloric acid and then placing it in a roaring Bunsen flame. This procedure should be repeated until the wire no longer produces a colour in the flame.
2. The end of the wire should then be dipped into fresh hydrochloric acid and then into the solid sample under test.
3. The end of the wire should then be placed into a non-roaring, non-luminous Bunsen flame.
Result: In the table below are some of the common metal cations that can be tested in this way:
Identifying the ammonium ion, NH 4
Test: Add aqueous sodium hydroxide to the solid, or solution, under test and warm the mixture. Result: If ammonium ions are present then a pungent-smelling gas is produced. The gas produced turns
damp red litmus paper blue. It is ammonia, NH3.
Equation:
Identifying metal cations by using precipitation reactions
Most metal hydroxides are insoluble and hence can be precipitated from aqueous solutions of metal salts by adding an aqueous solution of sodium hydroxide.
The technique is to add the reagent (i.e. the aqueous sodium hydroxide) a drop at a time to form the precipitate.
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Metal cation
Colour of flame
Lithium, Li
Red
Potassium, K
Lilac
Calcium, Ca2
Brick red
Sodium, Na
Yellow / orange
NH(aq) OH → NH HO 432
ammonium ions (from the solution being tested)
hydroxide ions (from the sodium hydroxide added)
Section B: Chemistry of the Elements

EXAMINER’S TIP
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Some common metal cations that can be identified using these reagents are shown in the table below:
The ionic equations given here apply to any combinations
of metal salt and sodium hydroxide. Although there
is no requirement in the specification to learn ionic equations for these reactions, it is far easier to do so than to try to remember or work out individual equations for each separate combination of metal salt and sodium hydroxide.
Metal cation
Observation(s) with aq. sodium hydroxide
Equation for reaction
copper(II), Cu2
blue precipitate
Cu2(aq) 2OH(aq) → Cu(OH)2(s)
iron(II), Fe2
green precipitate
Fe2(aq) 2OH(aq) → Fe(OH)2(s)
iron(III), Fe3
brown precipitate
Fe3(aq) 3OH(aq) → Fe(OH)3(s)
Identification of anions (negative ions)
Halide ions by precipitation with silver nitrate solution
Test: To an aqueous solution of the solid under test, add some dilute nitric acid followed by a few drops of silver nitrate solution.
Results:
Halide ion present
Observation
Equation for reaction
chloride ion, Cl
white precipitate
(of silver chloride, AgCl)
Ag(aq) Cl(aq) → AgCl(s)
bromide ion, Br
cream precipitate
(of silver bromide, AgBr)
Ag(aq) Br(aq) → AgBr(s)
iodide ion, I
yellow precipitate (of silver iodide, AgI)
Ag(aq) I(aq) → AgI(s)

Hope it helps

Answer 2

Answer:

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